“While we believe natural gas power will continue to grow in the North American truck market, the timing of the adoption of natural gas in long haul fleets preferring 15 liter engines is uncertain,” says Christy House, On-highway Marketing Communications Director for Cummins.

Westport bowed out in October 2013, halting orders for its 15-liter engine and unveiled its next generation technology in December, which will largely entail working directly with vertically integrated OEMs.

Cummins’ ISX 15 G was expected to enter limited production as soon as late this year.

Cummins announced plans for the engine mid-2012 citing coming demand in the marketplace. However, infrastructure support has been slow to develop nationwide, according to Roe East, General Manager, On-Highway Natural Gas Engines at Cummins.

“We believe the adoption of natural gas in long haul fleets will be paced by a variety of factors beyond the engine and include fuel tank technology and public fueling infrastructure,” House says, adding Cummins will re-evaluate the market for the ISX 15 G later this year.